OCXO stability at TCXO power and
package size
Rakon has developed the
world’s first
TC-OCXOs (temperature-compensated oven-controlled crystal oscillators),
designed to deliver the high stability of an OCXO from a device with
low power consumption, small size and light weight comparable to those
of a TCXO. Known as Triton it is capable of stabilities better than
±0.05 ppm over
operating temperature range, Rakon TC-OCXOs are aimed at mobile,
battery powered and remote applications such as GPS, satellite comms,
distress beacons and secure radio.
Ambient temperature variation is one
of the
main causes of frequency variation in a crystal oscillator. To overcome
this, Rakon TC-OCXOs use a hybrid combination of limited temperature
control, by use of an oven, and further reduction of the remaining
frequency error through Rakon’s proprietary Pluto temperature
compensation technology.
Previous attempts by various parties
to
combine temperature compensation with oven control have taken a crude
‘heating a TCXO’ approach — a heater has
been used to
reduce the temperature range seen by the TCXO. The result has been
oscillators with good power consumption but significantly inferior
stability to existing OCXOs.
Rakon’s TC-OCXO proprietary
approach
uses a miniature oven with crude temperature control to keep the
crystal oscillator at an approximately constant temperature slightly
above its specified operating temperature range — e.g.
between
90° and 95°C for a device with operating temperature
range
specified as –40° to +85°C. Any residual
frequency errors
occurring over the oven’s limited temperature range are then
minimized using the Pluto’s analogue compensation circuitry.
The result is an oscillator with
overall
stability nearly an order of magnitude better than the most stable
TCXOs — i.e. comparable to that of an OCXO — but
with
better power consumption, smaller and lighter package size and faster
warm-up. For example, a typical specification might offer
±0.05
ppm stability over temperature range of –20° to
+70°C, at
standard frequencies from 5 to 20 MHz, with a highly linear
±5
ppm frequency adjustment for ageing effects, power consumption
≤400
mW at –20°C steady state or ≤1.0 W during
warm-up, from a
3.3 V supply, in an industry standard 20.7 x 13.08 mm DIL package.
Related links:
Pluto
temperature compensation
Application
note: Quartz crystal resonators
Application note:
Timekeeping with quartz crystals
Application
note: Jitter
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